Vehicle seat assemblies are commonly constructed so that the seatback member pivots relative to the seat member. Such pivotal movement may be rearwardly and downwardly with respect to the seat member (hereinafter referred to as "reclining" of the seatback member), thereby to allow for adjustment of the inclination angle of the seatback member to an operator selected position, or may be forwardly and downwardly relative to the seat member, (hereinafter referred to as "dumping" of the seatback member), thereby to allow for ingress and egress from the rear passenger area of a two-door vehicle. Such pivotal movement of the seatback member relative to the seat member, whether reclining or dumping, is typically accomplished through the use of a pivoting hinge mechanism which pivotally joins the seat and seatback members one to the other. Such hinge mechanisms typically incorporate at least one latching mechanism which latches the seatback member so as to restrain it in place at a desired operative angle with respect to the seat member. Such prior art latching mechanisms may be in full time latching engagement to prevent unwanted reclining or dumping, in which case the seat occupant must manually release the latching mechanism to allow pivotal movement of the seatback member. Alternatively, such latching mechanisms may be of the well-known "inertial" type which latch under the influence of inertial forces generated during very rapid vehicle deceleration. An example of the former type of latch mechanism can be seen in Canadian Patent No. 1,293,681, issued to Bertrand Faure Ltd. on Dec. 31, 1991, and an example of the latter type can be seen in U.S. Pat. No. 4,707,010 issued to Croft on Nov. 17, 1987. The teachings of both the Bertrand Faure Ltd. and Croft patents are incorporated herein by reference.
Cost considerations in the construction of vehicle seat assemblies have tended to result in modern seat latching mechanisms becoming smaller than their predecessors so as to realize material savings to the manufacturer.
Weight reduction in modern vehicles has also become an important design consideration. In this regard, it has also become common to reduce the size of the latching mechanisms used in vehicle seat assemblies.
Further, size reduction is also being emphasized by vehicle designers as they request engineers to package the aforementioned latching mechanism in increasingly smaller design envelopes.
Another solution for cost and weight reduction has been for seat assembly manufacturers to utilize a full latching mechanism on only one side of a vehicle seat assembly. Such a single-sided latching mechanism must, however, be somewhat larger than a latching mechanism designed for tandem use on each side of a seat assembly in order to adequately provide for occupant loading during collision or collision-like conditions. Accordingly, this approach to cost and weight reduction is a limited one, particularly where small design envelopes are dictated by the vehicle or seat assembly design.
It will be appreciated that the lost strength and rigidity introduced into the seat assembly by downsizing and by single-sided latching, as previously described, may lead to deformation or breakage of the seat assembly components, including the latching mechanism itself, in vehicle collisions. This is especially likely in collision impacts from the rear of the vehicle, wherein the seatback member must accelerate the mass of the torso of the seat occupant during very rapid forward acceleration. Resultingly, the seatback member and the related latching mechanism must be designed to withstand the relatively larger forces encountered in rear impact collisions. Such uncontrolled deformation or breakage can result in serious injury to the seat occupant. In frontal vehicle impacts, it will be appreciated that the occupant's torso is thrown forwardly toward the dashboard of the vehicle, so that the accelerated mass of such occupant's torso is not borne by the seatback member. As the loading of the seatback member is not so severe in frontal impacts, single-sided latching may be adequate from a safety standpoint in such collisions. However, single-sided latching is more likely to be unacceptable from a safety standpoint in the case of collisions to the rear of a vehicle or during collision-like conditions wherein high accelerative or decelerative forces may be experienced, particularly where downsizing is an inherent necessity in the design of the single-sided latching mechanism utilized.
From a safety standpoint, therefore, it will be appreciated that it is desirable to avoid the use of single-sided latching, and employ a supplemental latching mechanism that latches the seatback member with respect to the seat member during conditions of rapid vehicle acceleration or deceleration, such as are encountered during collision or collision-like conditions. Inertial actuation of the supplementary latching device in collision or collision-like situations allows the device to be simple, lightweight and inexpensive to manufacture, as it eliminates the need for the connection of slave actuation hardware between it and the master latching mechanism, while at the same time providing for an increased level of safety to the seat assembly occupant, particularly where it is designed to be actuated in a rear vehicle collision.
Such supplemental latching mechanisms have not been commonly employed to date in vehicle seat assembly designs, particularly in relation to applications intended to address the problem of rear impacts as described above. To be practical, such supplemental latching members must be compact, lightweight, inexpensive to manufacture and assemble, and provide rapid positive interlocking latching against pivotal movement, whether reclining or dumping, of the seatback member. Moreover, such a supplemental seat latching mechanism should be inertially actuated, so as not to interfere with routine pivoting motion of the seatback member during use of the vehicle, as controlled by a master latching mechanism.
It is, therefore, an object of the present invention to provide a simple, lightweight and inexpensive inertial latching mechanism for use in a vehicle seat assembly having a seatback member that moves pivotally with respect to the seat member, for latching the seatback member with respect to the seat member in the event of a vehicle collision or under collision-like conditions.
It is a further object of this invention to provide an inertial latching mechanism that is ideally suited to be used as a supplementary latching mechanism to be used in tandem with a master latching mechanism of known design on a seat assembly on the opposite lateral side of the seat assembly from said master latching mechanism so as to augment the load bearing capability of the master latching assembly, particularly under conditions of rear collision.
It is a further object of the present invention to provide an inertial latching mechanism that, when used in a vehicle seat assembly as a supplementary latching mechanism that is to be actuated in rear collisions only, allows the use of a significantly smaller and lighter master latching mechanism on the opposite lateral side of the vehicle seat assembly.
It is a further object of this invention to provide an inertial mechanism that is not subject to unlatching by way of bounce out of the latching pawl, such as may occur under load lapse conditions, which arise, for example, during a sudden reversal of vehicle direction, as during a secondary vehicle collision.
It is yet a further object of this invention to provide an inertial latching mechanism that remains it its latched configuration once latched. This feature requires the seat assembly and the latching mechanism thereon to be inspected and serviced by a qualified mechanic or technician following an activating impact, so as to allow confirmation by such mechanism techniques of the structural integrity of the seat assembly and latching mechanisms prior to re-entering the vehicle into active service.